RNA-seq analysis of bovine adipose tissue in heifers fed diets differing in energy and protein content.

Hilde K L Wærp,Paul Cormican,Ragnar Salte,Matthew S Mccabe,Sinéad M Waters,Juan J Loor

doi:10.1371/journal.pone.0201284

Abstract

Adipose tissue is no longer considered a mere energy reserve, but a metabolically and hormonally active organ strongly associated with the regulation of whole-body metabolism. Knowledge of adipose metabolic regulatory function is of great importance in cattle management, as it affects the efficiency and manner with which an animal converts feedstuff to milk, meat and fat. However, the molecular mechanisms regulating metabolism in bovine adipose tissue are still not fully elucidated. The emergence of next-generation sequencing technologies has facilitated the analysis of metabolic function and regulation at the global gene expression level. The aim of this study was to investigate the effect of diets differing in protein and energy density level on gene expression in adipose tissue of growing replacement dairy heifers using next-generation RNA sequencing (RNAseq). Norwegian Red heifers were fed either a high- or low-protein concentrate (HP/LP) and a high- or low-energy roughage (HE/LE) diet from 3 months of age until confirmed pregnancy to give four treatments (viz, HPHE, HPLE, LPHE, LPLE) with different growth profiles. Subcutaneous adipose tissue sampled at 12 months of age was analyzed for gene expression differences using RNAseq. The largest difference in gene expression was found between LPHE and LPLE heifers, for which 1092 genes were significantly differentially expressed, representing an up-regulation of mitochondrial function, lipid, carbohydrate and amino acid metabolism as well as changes in the antioxidant system in adipose tissue of LPHE heifers. Differences between HPHE and HPLE heifers were much smaller, and dominated by genes representing NAD biosynthesis, as was the significantly differentially expressed genes (DEG) common to both HE-LE contrasts. Differences between HP and LP groups within each energy treatment were minimal. This study emphasizes the importance of transcriptional regulation of adipose tissue energy metabolism, and identifies candidate genes for further studies on early-stage obesity and glucose load in dairy cattle.

Highlights

The global human population is steadily increasing, and with it so are the demands for efficient animal production systems [1, 2]
Body condition scores were different between different energy treatments (p < 0.05), but not between protein treatments within an energy treatment
Dietary energy content has a massive impact on the bovine adipose tissue transcriptome regulating several aspects of energy metabolism

Summary

Introduction

The global human population is steadily increasing, and with it so are the demands for efficient animal production systems [1, 2]. Efficient meat and milk production is dependent on animals with a well-functioning metabolism and an efficient and purposeful nutrient allocation [3,4,5]. For growing cattle this implies a rapid growth rate without excess fattening, as the number of days spent to achieve productive size is proportional to total rearing costs [6], while excessive fattening has a negative impact on both feed efficiency, subsequent health and carcass value [5, 7]. The molecular mechanisms by which these effects are exerted are still not fully elucidated

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